RF front-end with wideband transmitter/receiver isolation

Abstract

Embodiments of a four-port isolation module are presented herein. In an embodiment, the isolation module includes a step-up autotransformer comprising a first and second winding that are electrically coupled in series at a center node. The first port of the isolation module is configured to couple an antenna to a first end node of the series coupled windings. The second port of the isolation module is configured to couple a balancing network to a second end node of the series coupled windings. The third port is configured to couple a transmit path to the center node. The fourth port is configured to couple a differential receive path across the first end node and the second end node. The isolation module effectively isolates the third port from the fourth port to prevent strong outbound signals received at the third port from saturating an LNA coupled to the fourth port.

What is claimed is: 
     
       1. A radio-frequency (RF) front-end comprising:
 an autotransformer comprising a first end node, a second end node, and a center node, wherein the autotransformer further comprises a primary winding and a secondary winding that are electrically coupled together at the center node; 
 an antenna coupled to the first end node; 
 a balancing network coupled to the second end node; 
 a power amplifier coupled to the center node; and 
 a low-noise amplifier coupled across the first end node and the second end node. 
 
     
     
       2. The RF front-end of  claim 1 , wherein the autotransfoimer and the balancing network are configured such that a signal provided by the power amplifier at the center node appears common mode to the low noise amplifier at the first end node and the second end node. 
     
     
       3. The RF front-end of  claim 1 , wherein the RF front-end is configured for full-duplex communication. 
     
     
       4. The RF front-end of  claim 1 , wherein the autotransformer is a step-up autotransformer. 
     
     
       5. The RF front-end of  claim 1 , wherein a ratio of a number of turns in the primary winding to a number of turns in the secondary winding is configured to be adjusted. 
     
     
       6. The RF front-end of  claim 5 , wherein the ratio is configured to be adjusted based on an insertion loss of the autotransformer between the antenna and the low-noise amplifier. 
     
     
       7. The RF front-end of  claim 5 , wherein an impedance of the balancing network is configured to be adjusted based on the ratio. 
     
     
       8. The RF front-end of  claim 1 , wherein an impedance of the balancing network is configured to be adjusted based on an impedance of the antenna. 
     
     
       9. The RF front-end of  claim 1 , wherein the low-noise amplifier is a noise-matched low-noise amplifier. 
     
     
       10. A radio-frequency (RF) front-end comprising:
 an autotransformer comprising a primary winding and a secondary winding, wherein the primary winding and the secondary winding are coupled in series at a center node; 
 an antenna coupled to an end node of the primary winding; 
 a balancing network coupled to an end node of the secondary winding; 
 a power amplifier coupled to the center node; and 
 a low-noise amplifier coupled across the end node of the primary winding and the end node of the secondary winding. 
 
     
     
       11. The RF front-end of  claim 10 , wherein a resistance of the balancing network is inversely proportional to a ratio of a number of turns of the primary winding to a number of turns of the secondary winding. 
     
     
       12. The RF front-end of  claim 11 , wherein the ratio is configured to be adjusted. 
     
     
       13. The RF front-end of  claim 12 , wherein the ratio is configured to be adjusted based on an insertion loss of the autotransformer between the antenna and the low-noise amplifier. 
     
     
       14. The RF front-end of  claim 10 , wherein the autotransformer and the balancing network are configured such that a signal provided by the power amplifier at the center node appears common mode to the low noise amplifier at the end node of the primary winding and the end node of the secondary winding. 
     
     
       15. The RF front-end of  claim 10 , wherein the RF front-end is configured for full-duplex communication. 
     
     
       16. The RF front-end of  claim 10 , wherein the low-noise amplifier is a noise-matched low-noise amplifier. 
     
     
       17. A radio-frequency (RF) front-end comprising:
 an autotransformer comprising a primary winding and a secondary winding, wherein the primary winding and the secondary winding are coupled in series at a center node; 
 an antenna coupled to an end node of the primary winding; 
 a balancing network coupled to an end node of the secondary winding; 
 a power amplifier coupled to the center node; and 
 a noise-matched low-noise amplifier coupled across the end node of the primary winding and the end node of the secondary winding. 
 
     
     
       18. The RF front-end of  claim 17 , wherein a resistance of the balancing network is inversely proportional to a ratio of a number of turns of the primary winding to a number of turns of the secondary winding. 
     
     
       19. The RF front-end of  claim 18 , wherein the ratio is configured to be adjusted. 
     
     
       20. The RF front-end of  claim 19 , wherein the ratio is configured to be adjusted based on an insertion loss of the autotransformer between the antenna and the noise-matched low-noise amplifier.